1. Field of Invention
This invention relates to a coupling mechanism for a refrigerant compressor, and more particularly, to a mechanism for disconnecting the drive shaft of the compressor from a drive pulley in the event of a compressor malfunction.
2. Description of the Prior Art
In the standard automotive air conditioning system, an electromagnetic clutch is interposed between the automotive engine and the drive shaft of the compressor to intermittently transmit the rotational driving force of the engine to the shaft. The operation of the electromagnetic clutch is controlled by a change in the operating conditions of the air conditioning system, for example, a change of temperature in the passenger compartment.
In the event of a compressor malfunction, the clutch should operate to disconnect the engine from the compressor to prevent transmission of the rotational driving force from the engine. However, since the clutch is usually loaded in a compressor which has a variable displacement mechanism, which enable the compressor to change its capacity in direct response to changes in operating conditions, the electromagnetic clutch is not necessary to obtain satisfactory control of the refrigeration or temperature condition of the air conditioning system. Nevertheless, it is necessary to provide the compressor with a safety mechanism to prevent damage to other parts of the engine or air conditioning system in the event of a compressor malfunction. The electromagnetic clutch serves as an expensive solution to this problem.
One example of an automotive air conditioning compressor system which has not made use of an electromagnetic clutch is disclosed in U.S. Pat. No. 3,861,829. As shown in the compressor of FIG. 1, pulley 1 is directly connected to the outer terminal end of drive shaft 3 and extends around the outer peripheral surface of tubular extension 2 of drive shaft 3. In this configuration, the rotational driving force of the engine is constantly transmitted to drive shaft 3 through pulley 1 via a drive belt (not shown). Since pulley 1 is never disconnected from drive shaft 3 even in the event of a compressor malfunction, such a malfunction is directly passed on to the driving system of the automobile. Damage on the engine and other parts of the driving system is likely to occur.